To provide a gas engine with an auxiliary chamber in which heat efficiency of the engine is improved, and occurrence of knocking is suppressed by uniformly mixing torch flame from the auxiliary chamber to a main combustion chamber, with the air and a lean mixture gas existing in the main combustion chamber by disordering a flowing field of the air and the lean mixture gas existing in the main combustion chamber.

A gas engine with an auxiliary chamber includes: turbulence promotion medium flowing-in means 53 for promoting turbulence of a flowing field in a main combustion chamber 7 by injecting a fluid different from a fuel gas into the main combustion chamber 7, in addition to combustion torch injected into the main combustion chamber 7 from an auxiliary chamber injection hole 35 of an auxiliary chamber 29 and an intake gas flowing into the main combustion chamber 7 from an intake port 9; and a medium inflow control device 59 for controlling a timing when the turbulence promotion medium is allowed to flow into the main combustion chamber on the basis of the relationship with an ignition timing of the fuel gas supplied into the auxiliary chamber 29.